1. Field of the Invention
This invention relates to a Ni--Zn type ferrite which is suitable for magnetic materials of an isolator and the like used in a millimeter wave frequency band in high frequency fields, small in dielectric loss, and high in saturated magnetization.
2. Description of the Related Art
A Ni--Zn type ferrite is one of typical ferrites which are suitable for device elements such as a circulator for communication and the like used in a microwave frequency band. Recently device elements such as a circulator and the like which act in a frequency range of tens to hundreds of GHz have been primarily developed. It is indispensable for such a device element to have not only high saturated magnetization (4.pi.M.sub.s), small ferromagnetic resonance absorption half width (.DELTA.H), and high Curie point, but also small dielectric loss (tan.delta.(.epsilon.)) to secure the reliability of the device. Therefore, there is a strong desire to develop materials with small dielectric loss (tan.delta.(.epsilon.)). In this situation, ferrites represented by the general formula: Li.sub.0.5-0.5x-0.5y Fe.sub.2.5-0.5x-0.5y Zn.sub.x Mn.sub.y O.sub.4 (0.15.ltoreq.x.ltoreq.0.45, 0.02.ltoreq.y.ltoreq.0.18) are proposed (Japanese Unexamined Patent Publication (Kokai) No. 61-51405). The conventional ferrites described in this publication are produced by substituting a part of the composition of a lithium ferrite, which is represented by the general formula: Li.sub.0.5 Fe.sub.2.5 O.sub.4, with Zn and Mn. With this conventional ferrite, high saturated magnetization (4.pi.M.sub.s) and dielectric loss (tan.delta.(.epsilon.)) of the order of 10.sup.-3 are attained.
With advanced densifying of information and the like, however, the development of ferrites, which can be used for device elements such as a circulator and the like utilized in a higher frequency GHz band, is more strongly desired. From this reason, the development of ferrites with a high saturated magnetization (4.pi.M.sub.s) and dielectric loss (tan.delta.(.epsilon.))of the order of 10.sup.4 is in large demand.